package com.hzlh.utils;

import java.io.*;

public class Base64Encoder  extends FilterOutputStream {
    private static final char[] chars = {  
        'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',  
        'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',  
        'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd',  
        'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',  
        'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x',  
        'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7',  
        '8', '9', '+', '/'  
       };  
         
       private int charCount;  
       private int carryOver;  
         
       /*** 
       * Constructs a new Base64 encoder that writes output to the given 
       * OutputStream. 
       * 
       * @param out the output stream 
       */  
       public Base64Encoder(OutputStream out) {
        super(out);  
       }  
         
       /*** 
       * Writes the given byte to the output stream in an encoded form. 
       * 
       * @exception IOException if an I/O error occurs
       */  
       public void write(int b) throws IOException {
        // Take 24-bits from three octets, translate into four encoded chars  
        // Break lines at 76 chars  
        // If necessary, pad with 0 bits on the right at the end  
        // Use = signs as padding at the end to ensure encodedLength % 4 == 0  
         
        // Remove the sign bit,  
        // thanks to Christian Schweingruber <chrigu@lorraine.ch>  
        if (b < 0) {  
          b += 256;  
        }  
         
        // First byte use first six bits, save last two bits  
        if (charCount % 3 == 0) {  
          int lookup = b >> 2;  
          carryOver = b & 3;        // last two bits  
          out.write(chars[lookup]);  
        }  
        // Second byte use previous two bits and first four new bits,  
        // save last four bits  
        else if (charCount % 3 == 1) {  
          int lookup = ((carryOver << 4) + (b >> 4)) & 63;  
          carryOver = b & 15;       // last four bits  
          out.write(chars[lookup]);  
        }  
        // Third byte use previous four bits and first two new bits,  
        // then use last six new bits  
        else if (charCount % 3 == 2) {  
          int lookup = ((carryOver << 2) + (b >> 6)) & 63;  
          out.write(chars[lookup]);  
          lookup = b & 63;          // last six bits  
          out.write(chars[lookup]);  
          carryOver = 0;  
        }  
           charCount++;  
         
        // Add newline every 76 output chars (that's 57 input chars)  
           if (charCount % 57 == 0) {  
             out.write('\n');  
           }  
       }  
         
       /*** 
       * Writes the given byte array to the output stream in an  
       * encoded form. 
       * 
       * @param buf the data to be written 
       * @param off the start offset of the data 
       * @param len the length of the data 
       * @exception IOException if an I/O error occurs
       */  
       public void write(byte[] buf, int off, int len) throws IOException {
        // This could of course be optimized  
        for (int i = 0; i < len; i++) {  
          write(buf[off + i]);  
        }  
       }  
         
       /*** 
       * Closes the stream, this MUST be called to ensure proper padding is 
       * written to the end of the output stream. 
       * 
       * @exception IOException if an I/O error occurs
       */  
       public void close() throws IOException {
        // Handle leftover bytes  
        if (charCount % 3 == 1) {  // one leftover  
          int lookup = (carryOver << 4) & 63;  
          out.write(chars[lookup]);  
          out.write('=');  
          out.write('=');  
        }  
        else if (charCount % 3 == 2) {  // two leftovers  
          int lookup = (carryOver << 2) & 63;  
          out.write(chars[lookup]);  
          out.write('=');  
        }  
        super.close();  
       }  
         
       /*** 
       * Returns the encoded form of the given unencoded string.  The encoder 
       * uses the ISO-8859-1 (Latin-1) encoding to convert the string to bytes. 
       * For greater control over the encoding, encode the string to bytes 
       * yourself and use encode(byte[]). 
       * 
       * @param unencoded the string to encode 
       * @return the encoded form of the unencoded string 
       */  
       public static String encode(String unencoded) {
        byte[] bytes = null;  
        try {  
          bytes = unencoded.getBytes("UTF-8");  
        }  
        catch (UnsupportedEncodingException ignored) { }
        return encode(bytes);  
       }  
         
       /*** 
       * Returns the encoded form of the given unencoded string. 
       * 
       * @param bytes the bytes to encode 
       * @return the encoded form of the unencoded string 
       */  
       public static String encode(byte[] bytes) {
        ByteArrayOutputStream out =
          new ByteArrayOutputStream((int) (bytes.length * 1.37));
        Base64Encoder encodedOut = new Base64Encoder(out);  
          
        try {  
          encodedOut.write(bytes);  
          encodedOut.close();  
         
          return out.toString("UTF-8");  
        }  
        catch (IOException ignored) { return null; }
       }  
         
       public static void main(String[] args) throws Exception {
        if (args.length != 1) {  
          System.err.println(
            "Usage: java com.oreilly.servlet.Base64Encoder fileToEncode");  
          return;  
        }  
         
        Base64Encoder encoder = null;  
        BufferedInputStream in = null;
        try {  
          encoder = new Base64Encoder(System.out);
          in = new BufferedInputStream(new FileInputStream(args[0]));
         
          byte[] buf = new byte[4 * 1024];  // 4K buffer  
          int bytesRead;  
          while ((bytesRead = in.read(buf)) != -1) {  
            encoder.write(buf, 0, bytesRead);  
          }  
        }  
        finally {  
          if (in != null) in.close();  
          if (encoder != null) encoder.close();  
        }  
       } 
}
